<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
     * {
        margin: 0;
        padding: 0;
    }

    .contain {
        display: flex;

    }

    .left {
        width: 800px;
    }

    .head {
        width: 80%;
        height: 200px;
        background-color: green;

    }

    .bann {
        width: 80%;
        height: 400px;
        background-color: yellow;

    }

    .content {
        width: 80%;
        height: 1500px;
        background-color: red;

    }

    .s {
        margin-bottom: 10px;
    }

    .top {
        width: 100px;
        height: 100px;
        background-color: pink;
        top: 360px;
        position: absolute;
    }

    .goback {
        display: none;
    }
</style>
<body>
    <div class="contain">
        <div class="left">
            <div class="head s">
                头部区域
            </div>
            <div class="bann s">
                区域
            </div>
            <div class="content s">
                主体部分
            </div>
        </div>
        <div class="right">
            <div class="top">
                <span class='goback'>返回顶部</span>
            </div>
        </div>

    </div>
</body>
</html>